Refrigeration control system



Sept. 22, 1942. A. B. NEWTON 2,296,534

REFRIGERATION CONTROL SYSTEM Filed Jan. 25, 1940 fluir/11011414 1B e5 5558 I 62 59A H [L 6o 33 f" pige r`se.) 1 C 78. nmnfor Z87 Alwin B.Newham..

Patented Sept. 22, 1942 toA Minneapolis-Honeywell Regulator Company.;Minneapolis, Minn., a corporation o! Dela- Application January 25, 1940,Serial No. 315.504

11 Claims., (Cl. (i2-4) This invention relates to a control system fore. refrigerating apparatus for accomplishing substantially the sameresults as are accomplished in application Serial No. 101,107 filed byWayland R. Miller on September 16, 1936.

IThe Wayland R. Miller application utilizes a starter for controllingthe load circuit to a compressor motor and this starter is controlled bycontrol circuits, one of the controlcircuits being a starting circuit'and another control circuit being a maintaining circuit -including amaintainng switch which is operated by the starter. Such an arrangementoperates satisfactorily but inasmuch as it needs a starter for thecompressor motor it is necessarily relatively expensive to build. f n

It is therefore the prime object of the invention to provide a controlarrangement of the type disclosed in the Wayland R. Miller applicationwhich does not require a starter for the compressor motor. thisinvention thesta'rting circuit and the main- -taining circuit act alsoas the load circuit for the compressor motor and a novel mechanism isutilized for operating the maintaining switch of the maintainingcircuit. In one form oi the invention the maintaining switch is operatedby According to the principles ot suction pressure in such a manner thatthe maintaining switch is closed when the suction pressure decreases andis opened when the suction pressure increases regardless of the actualvalue oi the suction pressure. 'I'hus the maintaining switch is closedwhenever -the compressor is op- Figure 3 is a schematic wiring diagramof the control arrangement of'Figure l; and

Figure 4 is a'schematic wiring diagram of another forxn of thisinvention.

Referring nowA to Figure l of the drawing, a-

compartment to be conditioned is designated at i.. A cooling coil in the'form of an evaporator ill is located in the compartment I0 forconditioning the medium therein. For purposes of il lustration it isassumed that the compartment I0 is a storage compartment such as awalk-in' bor. and that the evaporator ii is utilized for maintaining a`desired temperature condition therein. Reirigerant is circulatedthrough the evaporator ii by means of a reirigeratlng apparatusgenerally designated at i2; rIhe re'frigeratingapparatus may comprise acompressor It operated by an electric motor it. Compressed refrigerantis discharged from the compressor i3 through a high pressure line itinto a condenser I5. Condensed refrigerant is collected in a receiver iiand flows through a liquid line i8 into the evaporator ii. Evaporatedrefrigerant is withdrawn from the evaporator il` through a suction lineiii by the compressor i8. The flow of refrigerant to the evaporator i iis regulated by an expansion valve tfwhich may be of the thermostatictype connected by a capillary tube 2ito a bulb 22 located at the outletoi the evaporator ii. The thermostatic expansion valve 20 operates tomaintain a desired amountI of liquid Y refrigerant within the evaporatorii for cooling erating and is opened Whenever the compressor is notoperating. In another form of the invention the maintaining switch isoperated by al small electromagnet which is included inA both thestarting and maintaining load circuits, the arrangement being such thatthe maintaining switch is closed whenever the starting or maintainingload circuits are completed.

Other objects of this invention reside in the details of constructionand the combination of elements utilized in obtaining the desiredsequence of loperation. v i

Further objects vand advantages will become apparent to those skilled inthe art upon reference to the accompanying specication, claims anddrawing, in which:

Figure 1 is a diagrammatic illustration of one form of this invention;

Figure 2 is an enlarged detailed sectional view .frigerating apparatus.

purposes.v

The compressor motor it and hence the com'- pressor i0 are controlled bya controller generally designated at 2i responsive to the condition ofthe medium being controlled by the evaporator il, such as thetemperature 'within the compartment i0, and also by a unitary controlarrangement generally designated at 2t responsive to suction pressureand head The controller 24 responsive to the temperature within thecompartment Il may comprise a bel- I lows 2t charged with a volatilefluid for operatin a lever 21 against the action ci an adjustabletension spring 29. The lever Il in turn operates a mercury switch 2t andfor purposes oi illustration itis assumed that when the temperaturewithin the compartment Il rises to 42 the mercury switch 20 is closedand when the temperature decreases to 40 the mercury switch 20 isopened.

The unitary control arrangement Il may comprise a beilows 3i connectedby a pipe. l2 to the pressure oi the Arejustable tension spring 35.

suction line I9 so that the bellows 3 I'is expanded and contracted in'accordance with the suction pressure of the refrigerating apparatus. Thebellows 3| operates a lever 33 fulcrumed on a fulcrum member 34 againstthe action of an ad- One end of the tension spring 35 is connected tothe lever 33 and the other end is connected to a nut-36 screw threadedlymounted on a screw 31. By rotating the screw 31 the tension in thespring 35 may be varied to adjust the pressure settingof this portion ofthe unitary control arrangement.

A pair of levers 39 and 40 are carried by leaf springs 4I secured to abracket 42. The leaf springs 4I urge the levers 39 and 49 intoengagement with concentrically located and independently adjusted cams43and 4 4. The levers 39 i and 49 in turn carry snap action switches 45and 46 which maybe of the type shown and described in application SerialNo. 307,991 l'ed by Albert E. Baak on December 7, 1939. The snap actionswitches 45 and 46 are self-return switches and are provided withplungers 41 which are adapted to be engaged by a pad 48 carried by thelever '33. .The snap action switches 45 and 46 include' a single poledouble throw switch which is electrically connected to the-terminals-50, and 52.

When the plunger 41 of one of the switches is moved inwardly a circuitis completed across terminals 50 and 5| and when the plunger 41 isreleased this circuit is broken and one is completed across terminals 50and 52. Upon an in' crease in suction pressure the pa'd 48 engages theplungers 41 to move the plungers 41 inwardly to complete the circuitacross terminals 59 and 5|, i. e. to close thel snap switches 45 and 46.By rotating the cams 43 Aand 44 the pressure values at which .the'snapaction switches 45 and 46 operate may be varied. For purposes ofillustration it is assumed that upon an increase in suction-pressure thesnap switch 45 is rst closed at 20 lbs. and then the snap switch 46 isclosed at 35 lhs. Upon a decreasein suction pressure the snap switch46is iirst opened at v30 lbs. and then the snap switch 45 is opened at15 lbs.'

Another snap switch shown at 55 and this snap switch is'similar toswitches 45 and 46 with the exception that thel switch 56- is a twoposition 'switch requiring positive operation in both directions tosopenand close the switch. See Figure 5 -of the aforementioned Baakapplication.

a member 59 provided with eccentric screws 69 68 for urging the plunger58 into engagement with the member 59. 'I'he tension of the leaf spring62v may be adjusted by a. setfscrewv 63;

vupon a reversal in the trend o1' the suction prescreases andthelever-33 engages the eccentric screw 60 to close the snap switch 55. Afi.v rthe'r decrease in .suction pressurecauses slipping of theconnection between-*the member 59 and the plunger 58, the snap switch455 remaining closed.. lAs soon as the compressor I3 is stopped thesuction pressure increases to cause the lever 33 to engage the eccentricscrew 6 I and the snap switch 55 opens. pressure Lcauses slipping of.the connection between the member 59 and the plunger 58, the switchremaining open until such time as the compressor is again placed inoperation. For

, purposes' of illustration it is assumed that a de- The plunger 58thereof is frictionally engaged by and 6I which are engaged by the endof the lever '33. By referring to Figure 2 of the drawing it is seenthat a leaf spring 62 engages the plunger y 86 and 81 leading from somesource of power, not s crease of 3 lbs. suction pressure is required toclose the snap switch 5 5 land a 3 1b. increase in suction pressure isrequired to open the snap` switch 65. The 'differential in pressurerequired to openand close the snap switch 55 may be varied byadjusting'the eccentric screws 60 and 6I.

Theunitary control arrangement 25 may also comprisea bellows 65connected by a pipe 66 to the high pressure line I5 or the condenser I6so that the bellows 65 is operated in accordance Y with changes in headpressure. The bellows 65 operates a lever 61 ulcrumed on a fulcrummember 68 against the action of an adjustable tension spring 69. One endof the tension spring 69 is connected to the lever 61 and the other endis connected to a nut 18 screw threadedly mounted on a screw 1I, Byrotating the screw 1I the tension in the vspring19 may bef'varied toadjust the-pressure setting of this portion of the unitary controlarrangement.

A pair of levers 13 and 14 are carried-bythe I leaf springs 4I andthe'leaf springs 4|- urge the levers 13 and 14 into engagement withconcentrically located and independently adjustable ,t

cams 15 and 16.i The levers 13 and 14 carry snap switches 11 and 18which are-similar in construction to the'snap switches 45 "and 46. Thesnap. switches 11 'and 18 are provided with plungers' 19 which areadapted to be engaged by a -pad 8|)A carried by the lever 61. Upon anincrease in 'head pressure, the pad 89 engages'the plungers 19 of thesnap switches 11 and 18 to break the circuit, across the terminals 50'and 52, i. e., open the snap switches 11 and 18. Upon a decrease inhead pressure the pad releases the plunger 19 Yto completethecircuits'across the terminals 50 and 52 of the snap switches 11 and18, i. e., close the snap switches 11 and 18. For purposes ofillustration, it is assumed that upon an increase in head pressure thesnap switch 11 is iirst opened at pounds and then the snap switch 18 isopened at pounds. Upon a. decrease in head pressure the snap switch 18.i5 first closed at 185 lbs. and then the snap switc'h 11 is closed at135 pounds. I

Power is supplied to .the compressor motor I4 and to the control systemby lmeans of line .wires shown.

s ure. For example, assume'that the compressor I3 is not operating andthat' the switch 55 is opened. As soon as the compressor is placed inoperation the suction pressure immediately de- With the parts intheposition shown in Figurev 1, the compressor I3 is not operating and themercury switch 29 of the temperature controller 24 is operi.- Assume nowthat the head pressure is below 135 pounds whereupon the snap lswitches11 and 18 are closed and that the suction pressure rises to 35 poundswhereupon the snap switches 45 and 46 are closed. When the temperaturewithin the compartment Ill rises to42, a starting load circuit iscompleted from the line wire 86 through snap switch 18, wire 88, snap Afurther increase in suction completing the maintaining load circuit.

switch 45,w1res a9 and so, snap 'switch as, wire 9|, snap switch 11,wires 92 and 83, mercury switch 29, wire 94, and compressor motor |4back to the other line wire 81. Completion of this starting load circuitcauses operation of the compressor motor I4 and hence operation of thecompressor I3.

As soonl as the compressor I3 is thus placed in operation, the suctionpressure immediately decreases sufiiciently to cause the sna'p switch 55to close. Snap switch 55 closes before snap switch 46 opens. Closure ofthe snap switch 55 establishes a maintaining load circuit which isindependent of the snap switches 46 and 11 for maintaining thecompressor in operation even though the suction pressure decreases belowpounds or the head pressure increases above 140 pounds. This maintainingload circuit may be traced from the line wire 86 through snap switch 18,wire 86,

snap switch 45, wires 8a and 96, snap switch 55,

maintaining circuit is broken and the compressorV motor I4 and hence thecompressor i3 are stopped. Immediately upon stopping of the compressorI3 the suction pressure .rises sufficiently to cause the snap switch55.to open. It is therefore impossible to vrestart the compressor 'afterit has once stopped until the above starting load circuit is againreestablished and this may occur only when the mercury switch 29 of thetemperature responsive controller 24'closes, the suction pressureincreases to pounds to close the snap switch 46 and the head pressuredecreases to 135 l pounds to close the snap switch 11.

From the above, it is seen that I have provided a control arrangementwherein a compressor is started only when the temperature within thecompartment rises to a, predetermined high value, the suction pressurerises to a predetermined high value, whichvalue may be a defrostingvalue, and the head pressure decreases to a predetermined low value.

the temperature within the compartment decreases to a predetermined lowvalue or the suction pressure decreases to a predetermined low value orthe head pressure increases to a predetermined high value. In carryingout this invention, it is seen that separate control` circuits and loadcircuits -for the compressor are not needed and that the starterfoi-,the compressoris eliminated. A novel switching arrangement operatedupon changes insuction pressure regardless of the actual value thereofis utilized for By reason of the arrangement of this invention,substantially the same results are obtained -as are obtained in the'above referred'to Wayland R.; Miller application in an improved and lessexpensive manner. l

Figure 3 shows schematically the wiring arrangement utilized m Figure 1.Instead of utilizing the slip friction operated mi'iintaining switch 56of Figures 1 and23 for completing the maintaining load circuit, adifferent maintaining switch may be utilized such a'sillustrated inFigure 4. Here an electromagnetic switch is'illtis- After the compressorhas once been started it will remain in operation until either trated at|00 and it comprises an operating coil IIII for moving a switch arm |02into engagement with a contact |03 when the operating coil I0|l isenergized. When the operating coil I0| is deenergized, the switch arm|02 is moved out of engagement with the contact |03 by means of springs,gravity or other means, not shown. The switch ,arm |02 and the contact|03 vform vthe maintaining switch which is in parallel with the snapswitches 46 and 41 and the operating coil |0| is included in both thestarting and maintaining load circuits. The operation of the arrangementof Figure 4 is therefore exactly the same as that of Figures 1 and 3 andtherefore a further description thereof .is not considered necessary.

Although for purposes of illustration one form of this invention hasbeen disclosed, other forms thereof may become apparent to those skilledin the art upon reference to this disclosure andl therefore thisinvention is to be limited only by the medium being controlledindicative of a need, for compressor operation for opening and closingkthe first switch, a second switch, means responsive to suction pressurefor closing the second switch when the suction pressure increases to apredetermined high value, a third switch, means'responsive to suctionpressure for opening the .third switch when the suction pressuredecreases to a predetermined' low value, a fourth switch,means`operative as an incident to operation of the compressor for closingthei fourth switch, a startingv load circuit through the electriccompressor' motor including the rlrst, second and third switches and theelectric compressor motor in series, and a maintaining load circuitthrough the electric compressor motor including the first, thirdandfourth switches and the electric compressor motor l in series.

2. In a. refrigerating apparatus having an evaporator for controllingthe condition of a medium, acompressor for circulating refrigerantthrough the evaporator and an electric motor for'operating thecompressor, in combination therewith, a nrst switch, means responsive toa condition of the medium being controlled indicative of the need forcompressor operation for opening and closing the first switch, a secondswitch, means responsive "to suction pressure for closing the secondswitch when the suction pressure increases to a predetermined highvalue, a. third switch, means responsive to suction pressure for openingthe third switch when the suction pressure decreases to a predeterminedlow value, a fourth switch, meansvresponsive to head pressure for el thefourth switch when the head pressure decreases to a predetermined lowvalue, a fifth switch, means responsive to head pressure for opening thefifth switch when the head pressure increases to a predetermined highvalue, a sixth switch, means operative as an incident to operation ofthe compressor for closing the sixth4 third, fifth and sixth switchesand ,the electric compressor motor in series.

3. In a refrigerating apparatus having an evaporator for controlling thecondition of a medium, a compressor for circulating refrigerant throughthe evaporator and an electric motor for operating the compressor,v incombination therewith, a

' ilrst switch, means responsive to a condition of the medium beingcontrolled indicative ofthe need for ,compressor operation for openingand closing the first switch, a second switch, means responsive tosuction pressure for closing the second switch when the suction pressureincreases to a predetermined high value, a third switch, a

starting load circuit through the electric compressor motor includingthe rst and second switches and the electric compressor 'motor -inseries, va maintaining load vcircuit through the electric compressor'motor including the nrst and third switches in series and the electriccompressor motor in series, an electromagnet in both the starting andmaintaining load circuits for closing the third switch when either'loadcircuit is completed. f

4. In a refrigerating apparatus having an evaporator for controlling thecondition of a medium,

cluding the first, third, fifth and sixth switches and the electriccompressor motor in series, an electromagnet in both the starting andmaintaining load circuits for closing the sixth switch when either loadlcircuit is completed.

6. In a refrigerating apparatus having an Vevaporator for controllingthe condition of .a medium, a compressor for circulating refrigerant4 Dthrough the evaporator and an electric motor for operating thecompressor, in combination therewith,V a first switch, means responsiveto a condition of the medium being controlled indicative of the need forcompressor operation for opening and closing the rst switch, a secondswitch, means responsive to head pressure for closing the second switch4when the head pre'ssure decreases to a predetermined low value,a

third switch, means responsive to head pressure for opening the secondswitch when', the head pressure increases to a predetermined high value,a fourth switch, means operative as an incident y to operation of thecompressor for closing the a compressor for circulating refrigerantthrough ing the compressor, in combination therewith, a first switch,means responsive-to the condition of the medium being controlledindicative of the need for compressor operation for opening and closingthe first switch, a second switch, means responsive to suction pressurefor closing the second switch when the suction pressure increases to apredetermined high value', a thirdswitch, means responsive to suctionpressure for opening ,the third switch when the suction pressuredecreases to a predetermined low value, a fourth switch, av

vstarting load circuit through the electric compressor motor includingthe first, second and third switches and the electric compressor-motorin l series, and a maintaining load circuit through the electriccompressor motor including the iirst, third and fourth switches and theelectric compressor motor in series, an electromagnet in both f theevaporator and an electric motor for operatfourth switch, a startingload circuit through the electric compressor motor including the rst,second and third switches and the electric compressor motor in series,and a maintaining 4load circuit through the electric compressor motorincluding the flrst, third and fourth switches and to Va predeterminedlow value, a third switch,

the starting and maintaining load circuits for closing the fourth'switch when either load circuit is completed. 1

5.'In a refrigerating apparatus having an evaporator for controlling thecondition of a medium, a compressor for circulating refrigerant throughthe evaporator andan electric motor for operating the compressor, incombination ltherel with,a first switch. means responsive to a con-,dition of the medium being controlled indicative fof the need forcompressor operation'for opening and closing the first switch, a secondswitch, means responsive to suction pressure for closing the secondswitch whenthe suction pressure increases to a predetermined high value,a third switch, means responsive to suction pressure for opening thethird switch when the suction pressure d to a predetermined low value,aA

fourth switchfmeans responsive to head pres-'- sure for closing thefourth switch when the head pressure decreases to a predetermined lowvalue,

a fifth switch, means responsive to head, pressure for opening the fifthswitch when the head pressure increases to a predetermined high value,

, a sixth switch, a starting'load circuit through f the electriccompressor motor including the rst,

second and fourth switches and the electric' compressor motor in series,a maintaining load circuit through the electric compressor motor inmeans responsive to head pressure for opening the second switch -whenthe head pressure increases to a predetermined high value, a fourthswitch, a starting load circuitthrough the lelectric compressor motorincluding the rst, second and third switches and the electriccompressory motorin series, and a' maintaining load circuit through theelectric compressor motor including the iirst,'third and fourth switchesand the electric compressor motor in series, an electromagnet in boththe starting and maintaining load circuits for closing. the fourthswitch when either load circuit is completed. A

8. In a refrigerating apparatus having evaporator for controlling thecondition of a medium and an electrically controlled com. pressor forcirculating refrigerant through the evaporator, in combinationtherewith, first switch means, means responsivevto -a condition of themedium being controlled by the evaporator in-A, dicative of theneed forcompressor operation for opening and closing the'iirst switch means,second switch means, means ,responsive to suction pressure for closingthe second switch meansvonly when the suction pressure increases to apredetermined high value, third switch means, 'means operative upon adecrease m suction pressure for closing the third switch means andforopening the third switch means upon an increase in suction pressureregardlesof' the `actual 'value ofA the suction pressure, a. startingcircuit 'foi-the electrically controlled mmpressor including the, firstand second switch` means in series, and amaintaining circuit for theelectrically controlled` r accessi compressor including the rst andthird switch means in series.

`9. In a refrlgerating apparatus having an evaporator for controllingthe condition of a medium and an electrically controlled compressor forcirculating refrigerant through the evaporator, in combinationtherewith, iirst switch.

means, means responsive to a condition ofthe medium being controlled bythe evaporator indicative oi the need for compressor operation foropening and closing the first switch means. second switch means. meansresponsive to suction pressure for closing the second switch meansmeans,meansoperativeuponainsuc tionpresureforclosingthefourthswitchmeansandforopeningthefourthswitchmeansupon anincreaseinpressureregoftheactualvalue of the suction pressure, a starting circuit for the electricallycontrolled compressor includingtheiirstandsecondswitchmeansin series,vand a maintaining circuit for lthe electrically controlled compressorincluding the third and fourth switch means in series.

l1. In a refrigerating apparatus having' an vevaporator for controllingthe condition of a only when the suction pressure increases to a Atheelectrically controlled compressor including the first, third and fourthswitch means in series.

10. In a refrigerating apparatus having an evaporator for controllingthe condition of a medium and an electrically controlled compressor forcirculating refrigerant through the evaporator, in combinationtherewith, ilrst switch means, means responsive to a condition of themedium being controlled by the evaporator indicative of the need forcompressor operation for opening'and. closing the first switch means.second switch means. means responsive to head pressure for closing thesecond switch means only when the head pressure decreases to apredetermined low value, third switch means, means responsive to headpressure for opening the third switch means when the head pressureincreases to a predetermined high value, fourth switch fourth switchmeans,mean`s presslneforclosingthefourthswitchmeansmly medium and anelectrically controlled compressor for circulating refrigerant throughthe evaporator, in combination therewith. first switch means, meansresponsive to a condition of the medium being controlled by theevaporator indicativeof the need for compressor operation `for openingand clam the first switch means,

second switch means, means responsive to suction pressure for closingthe second switch means onlywhenthesuctlonpresureincreasestoapredetermined high value. third switch means, means responsive to.suction pressure for opening the third switchvwhentheheadpresuretoapredete'rminedlowvulue,iii'thswitchmeans,meansYresponsivetoheadpressureforopenmgthenfth switchmeanswhenthehesdpressureincreases toapredeterminedhighvalue.sixthswitclrmeans,meansoperative uponadecreaseinsuctionpressureiorclosingthesixthswitchmeansandforopeningthesixthswitchmeansuponnu'increaseinpressurengardlessoftheactuslvalueseries,andamaintainingcircuitfortheelectr-i-Athe-suction Y

